OUTLINE  INTRODUCTION  OBJECTIVES  JUSTIFICATION  DRYING PRINCIPLE  DESCRIPTION OF VERSIONS A & B

Dryer are essential in most agrarian or industrial environments. This is because it effects efficient removal of water in items that needs to reduce or remove water e.g. agricultural products like grains, vegetables etc. Drying is a complex operation involving transient transfer of heat and mass. It occurs by effecting vaporization of water by supplying heat to the wet product. The heat may be supplied by convection, conduction or radiation.

Movement of the water within the products may occur due to one or more of these:-  Liquid diffusion, if the wet solid is at a temperature below the melting point of the liquid  Vapor diffusion, if drying takes place at a very low temperature and pressure as in freeze drying.  Surface diffusion.  Hydrostatic pressure differences where internal vaporization rate exceeds the rate of vapor transport through the solid to surroundings.  Combination of above mechanism.

OBJECTIVES The objectives of this design are: a)To produce a dryer that conserves energy consumption for optimal utilization. b)To produce an affordable dryer in terms of acquisition and operating cost. c)To produce a dryer with optimal local content and versatility.

JUSTIFICATION Product drying is essential in many areas of our endeavors in this life. In Nigeria, we need dryers a lot because of our high post harvest loses, high costs of importing dryers now makes it not available making it essential to develop local alternatives.

DRYING PRINCIPLES The purpose of a dryer is to remove moisture from a material or feedstock. This is done by converting a solid, semi – solid or liquid feedstock into a solid product by evaporation of the liquid into a vapor phase by application of heat. One of such methods is the use of hot air to suck up moisture in a product. The ease with which moisture is removed from any material is dependent on the surface area and the amount of restraint to removal of the water. Whereas different materials have different particle sizes. A typical summary of particle sizes is shown in table 1.

Ψ scaleMean size range (mm) Went worth range (inches) NameOther namesTypical products -8 to ω256 to ω10.1 to ωBouldersMinerals -6 to -864 to to 10.1CobblesPebblesFruits Yeast -5 to -632 to to 2.5GravelPebblesTomatoes -4 to -516 to to 1.26Medium gravel PebblesPepper -3 to -48 to to 0.63Medium gravel Beans -2 t0 -34 to to 0.31Fine gravelGround peanut -1 to -22 to to o.137 Very fine gravel 0 to -11 to to Very coarse sand 1 to 00.5 to to 0.039Coarse sand 2 to to to 0.02Medium sand 3 to 2125μ to 250μ to Fine sandCassava flour 4 to 362.5μ to 125μ to Very fine sandmud Table 1: Particle size chart from W. C. Krumblein and L. L. Sloss

DESCRIPTION OF VERSIONS A & B